Embedded non-volatile memory (ENVM), particularly memory which has bidirectional write current capability (also referred to herein as a “bidirectional current memory device”), is becoming increasingly popular as a storage solution. Some examples of ENVM devices include phase change random access memory (PCRAM) and spin torque transfer magnetic random access memory (STT-MRAM). Area density and isolation of memory cells are two issues for ENVM and bidirectional current memory device technology.
Bidirectional current memory devices are common to have multiple columns, each column with one or more bit lines, and multiple rows, each row with and one or more source lines and one or more word lines. Through this architecture, the memory may be read, written, or erased and, as an example, may be erased with a bit line high, source line low, or vice versa. However, in certain configurations there is a gate-to-source voltage drop across the access transistor during access. To compensate for this voltage loss, there is typically a need to overdrive the access gates/transistors. This often requires a charge pump or other device to provide the overdriven voltage. Additionally, according to certain developments in ENVM technology, the source line may be shared with access transistors of adjacent memory cells, which leads to the source line being generally perpendicularly aligned to the bit line and thus unnecessarily providing current to memory cells that are not being accessed.